Vibration signals measured by means of sensors arranged at or near components of a wind turbine are very efficient for the purpose of monitoring the health condition of the wind turbine. Accordingly, vibration signals have been widely used for decades in machine condition monitoring and fault diagnostics. However, in wind turbine industry, wide variations of geographical location weather conditions exist. Furthermore, wind turbine systems are complex and require several vibration signals in order to monitor the health of a wind turbine. Accordingly, a vast amount of data is required in order to monitor the health of a wind turbine, and the required amount of data is even larger in the case that a large wind turbine population, such as a wind farm, is monitored. As a result, the usual technology of comparing the vibration signal to a reference value in order to establish if a monitored wind turbine component is normal or abnormal is not practical or efficient.
US 2005/0284225 A1 discloses a system and a method for monitoring the condition of a drive train of a wind turbine. The condition monitoring system comprises at lease one vibration sensor located on a gearbox casing. A processing unit is coupled to the vibration sensor and is configured to receive signals representative of the detected vibrations from the vibration sensor. The processing unit may be operable to process the signals representative of detected vibrations of gears and bearings and to compute at least one dynamic energy index or location of fault. Each normalized dynamic energy index corresponds to a defined frequency band, which in turn corresponds to a particular gear set or the bearings. The normalized dynamic energy index is compared to predetermined reference values to determine if a fault is present in either the gear sets or the bearings.